Known curable resin compositions such as, e.g., epoxy resin compositions used for manufacturing parts of electronic devices, seals for electronic and electrical elements, adhesive agents, etc., are characterized by a high modulus of elasticity and stiffness in the cured state. Therefore, when such a resin is cured, the electronic and electric devices sealed with the use of the aforementioned resin develop high stress caused by thermal expansion of the resin. Such stress, in turn, causes bowing in electrical and electronic elements and substrates, formation of cracks in the cured resin itself, deterioration in the electronic and electrical parts, or formation of gaps between the parts and the cured resin.
In order to reduce the stress in a cured resin, it has been proposed to prepare a curable resin composition by combining the aforementioned curable resins with epoxy-containing silicone resins (see. Japanese Unexamined Patent Application Publication (hereinafter referred to as (Kokai) H5-295084 equivalent to EP0567079A1), a die-attach paste that is a product of a reaction between an epoxy resin, cyanate resin, and an epoxy-containing dimethylsiloxane compound (Kokai 10-147764; Kokai 10-163232), a die-bonding material obtained as a result of a reaction between an epoxy-containing silicone and phenol-type organic compound (Kokai H7-22441, Kokai H7-118365, Kokai H10-130465), etc. However, the aforementioned compounds produce a stress-release effect that is still insufficient, and therefore these compounds have found only limited application in electrical and electronic parts.
It is known that products obtained from curable silicone compositions are characterized by excellent dielectric properties, volumetric resistivity, resistance to insulation breakdown, etc. From the point of view of these electrical properties, the curable silicone compositions are attractive for use in electrical parts, electrical and electronic seals, adhesives, and the like. On the other hand, products obtained by curing the curable silicone compositions are soft and are characterized either by a high coefficient of thermal expansion or low strength and modulus of elasticity with insufficient protective capacity for electronic and electrical parts, as well as by low resistance to externally applied impact forces. Furthermore, low adhesiveness of the cured products to electrical and electronic parts and elements, results in the formation of gaps between the cured resin and the surfaces of the aforementioned parts and elements. In order to reduce coefficients of thermal expansion inherent in soft cured bodies, their compositions are combined with fillers. However, addition of the fillers sharply increases modulus of elasticity, so that the molded products loose their softness and flexibility. Thus, the improvement effects are very limited.
Furthermore, Kokai H6-306084 describes a short-time-gelation curable silicone composition composed of an epoxy-modified silicone oil and a phenol-modified silicone oil. However, this resin composition is inferior to others in curability and requires longer time for curing.